The invention relates to a driving scheme for a liquid crystal display. A passive matrix driving scheme is commonly adopted for driving a liquid crystal display. The minimise crosstalk, variations such as APT and IAPT are proposed. However, even with those improved methods, passive drive still results in high crosstalk and low contrast of the display. For those high-mux displays with liquid crystals of fast response, the problem of loss of contrast due to frame response is severe. To cope with this problem, active addressing was proposed in which orthogonal Hadamard matrix is used as the common driving signal. Each pixel is selected throughout the frame and the frame response effect becomes minimal. However, the method suffers from the problem of high computation and memory burden. Even worse, the difference in sequences of the rows of matrix results in different row signal frequencies. This may result in severe crosstalk problem. On the other hand, a variation of the active driving scheme exists, where the common driving matrix is chosen to be a block diagonal matrix made up of low order Hadamard matrices. The resulting square matrix is still orthogonal and the problems of high sequency and computation are relieved. By selecting different orders of the Hadamard building blocks, a Multi-Line-Addressing (MLA) scheme makes a compromise between frame response, sequency, and computation problems. Unfortunately, since the number of lines selected at a time is limited by the low order of the Hadamard building blocks, frame response persists.
It is an object of the invention to seek to provide a new matrix-driving scheme.
According to the invention there is provided a driving scheme for liquid crystal display of any order a dimensuion, comprising matrix building blocks posesing Orthogonal and Shift Orthogonality (SO) properties.
It will be understood that shift orthogonality refers to the property that the matrix is orthogonal to the column-shifted version of itself.
Thus, Shift Orthogonality (SO) is imposed to the common driving signal. As a result, the building blocks of the matrix become rectangular paraunitary matrices. Due to the SO property of those matrices, overlapping of the building blocks is allowed. Thus let the matrix be qxr, q and r being integers and q greater than r. r can be any integer multiple of q. For instance, if q=2, we can identify paraunitary matrices with r=4, 6, 8, . . . For q=3 we have r=6, 9, 12, . . . The value r is analogous to the order of the conventional MLA. It can be shown that an order-r paraunitary matrix performs similarly to an MLA-r in terms of voltage selection and bias ratios.
It will be understood that a paraunitary matrix is both orthogonal to itself and orthogonal to a column-shifted version of itself to any integer multiple of M. Using such a matrix the driving scheme out-performs MLA of the same order in terms of lower hardware complexity, less crosstalk, higher contrast and better viewing cone, and higher flexibility of implementation.